My last PSU I had for 4.5 years, well I still have it but I moved it to my testing rig when I was bought new main computer.
Its performance is 550W(upgrade from 420W) but it's still nowhere near its peak as I don't play games at all, so my rig, including 2 screens and speakers consume 200W at best. That's probably 100W load on the PSU which is not much.
The brand is LC Power, which is not as awesome as corsair or FSP or seasonic, but previous unit from them proved 100% reliability to me and I decided to get another one from them as well, it has been another year and 3 months, no problems so far.
And I don't plan to change PSU nor computer for a long time, the development very slowed and I find that everyone with i5 quad core CPU or more+equivalent graphics card still has good overkill over what games and demanding programs require.